Hepatitis C virus (HCV) is the leading cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). HCV chronically infects approximately 4 million people in the U.S. and 170 million people worldwide. HCV co-infection with HIV is very common with overall 25-30% of HIV-positive persons, particularly among drug abusers with up to 70% co-infection (2). HCV infection is a major risk factor for HCC development. HCV- associated end-stage of liver diseases is the leading indication for liver transplantation. Advances on HCV research have been significantly hampered by the lack of a robust cell culture HCV propagation system and reliable small animal models of HCV infection and replication. Recent breakthroughs have been the development of robust cell culture systems for replication of HCV replicon RNAs and production of infectious HCV, which allows genetic studies of the entire HCV life cycle. However, development of small animal models of HCV infection and replication is challenging and that the lack of a reliable small animal model represents a major barrier to HCV research. Recently, we have demonstrated that genotype 2a HCV RNA replicated efficiently in mouse embryonic fibroblasts (MEF) albeit inefficiently in mouse hepatocytes. More importantly, we have demonstrated that the cDNA-derived HCV RNA inside the cell resulted in robust production of infectious HCV. A recent study by Charlie Rice's group has demonstrated that the expression of human CD81 and occludin in mouse hepatocytes is essential and sufficient for infection of HCV pseudotyped particles. These remarkable advances provide a firm foundation to develop novel transgenic mouse models of HCV infection and replication. We hypothesize that cell type-specific cellular proteins are important for efficient HCV RNA replication and that transgenic mice expressing human CD81 and occludin in hepatocytes are susceptible to HCV infection. The overall goal of this exploratory research proposal is to develop novel transgenic HCV mouse models. Specifically, we will 1) identify cellular proteins important for efficient HCV RNA replication in mouse cells using proteomics, biochemical, and genetic complementation approaches (Specific Aim 1);2) develop novel transgenic mice that either contain full-length cDNAs of luciferase-expressing JFH1 HCV RNAs or express both human CD81 and occludin under the control of a liver-specific promoter (Specific Aim 2);and 3) determine HCV infection and replication in transgenic mice using luciferase-expressing HCV in conjunction with the administration of mouse interferon and HCV NS3 protease- and NS5B polymerase-specific inhibitors (Specific Aim 3). The successful development of transgenic HCV mouse models will represent a paradigm shift in the field of HCV research and will allow us to determine the roles and mechanisms of action of viral and cellular proteins in HCV infection, replication, pathogenesis, and carcinogenesis as well as the effects of illicit drugs and alcohol on HCV replication and pathogenesis. Additionally, transgenic HCV mouse models will facilitate the anti-HCV drug discovery and HCV vaccine development to eventually control HCV infection. PUBLIC HEALTH RELEVANCE: Hepatitis C virus (HCV) infection remains a major global health problem, affecting approximately 170 million people worldwide and 4 million Americans. Our overall goal of this research proposal is to develop novel transgenic HCV mouse models for the determination of the molecular mechanisms of HCV replication, pathogenesis, carcinogenesis, and the effects of illicit drugs and alcohol on HCV replication and pathogenesis. Additionally, transgenic HCV mouse models will facilitate the antiviral drug discovery and vaccine development to eventually control HCV infection.